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Twin threat: Cascadia and San Andreas faults may be seismically linked

Peer-Reviewed Publication

Oregon State University

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Chris Goldfinger, a marine geologist at Oregon State University, with sediment cores.

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Credit: Sean Nealon. Oregon State University

CORVALLIS, Ore. – Two fault systems on North America’s West Coast – the Cascadia subduction zone and the San Andreas fault – may be synchronized, with earthquakes on one fault potentially triggering seismic events on the other, a new study found.

“We’re used to hearing the ‘Big One’ – Cascadia – being this catastrophic huge thing,” said Chris Goldfinger, a marine geologist at Oregon State University and lead author of the study. “It turns out it’s not the worst case scenario.”

Goldfinger and a team of researchers drilled deep-sea sediment cores representing 3,100 years of geologic history, and analyzed layers known as turbidites that are deposited by underwater landslides often triggered by earthquakes. They compared turbidite layers in cores from both fault systems and found similarities in timing and structure, suggesting the seismic synchronization between the faults.

In most cases, it’s difficult to determine the time separation between the Cascadia subduction zone and northern San Andreas fault ruptures, but Goldfinger said there are three instances in the past 1,500 years, including a most recent one from 1700, when the researchers believe the ruptures were just minutes to hours apart.

The findings have significant implications for hazard planning, he said.

“We could expect that an earthquake on one of the faults alone would draw down the resources of the whole country to respond to it,” Goldfinger said. “And if they both went off together, then you’ve got potentially San Francisco. Portland, Seattle and Vancouver all in an emergency situation in a compressed timeframe.”

Geologists have hypothesized for several decades that faults could synchronize, but there has only been one observed example of the phenomenon – in Sumatra, three months apart in 2004 and 2005.

Goldfinger has been focused on the question for decades. In fact, the origins of the just-published paper date back to a 1999 ocean research cruise. Goldfinger and the research team were drilling sediment cores in the Cascadia subduction zone off the coast of Oregon and northern California, but a navigational error took them off course, about 55 miles south of Cape Mendocino in California and into the San Andreas zone.

They decided to drill a core in that area. Subsequent analysis of the core revealed a unique structure. Turbidites have a typical layering pattern, with coarser sediment on the bottom and fine-grained sediment on the top. But the researchers found the opposite pattern in this core: coarse, sandy sediment at the top and finer, silty sediment at the bottom.

This led them to conclude the fine-grained layer at the bottom was caused by a large earthquake on the Cascadia subduction fault and the coarser sediment at the top was caused by subsequent movement on the nearby San Andreas.

They then used radiocarbon to date the turbidite layers of that core and others they collected north and south of Cape Mendocino, the location where the northern San Andreas and Cascadia subduction zone faults converge.

That further analysis made it clear that the formation of that unique upside-down layering, which they call “doublets,” is best explained by earthquakes on both systems spaced closely in time, as opposed to aftershocks or other causes.

Other authors of the paper are: Ann Morey, Christopher Romsos and Bran Black of Oregon State’s College of Earth, Ocean, and Atmospheric Sciences; Jeff Beeson of the National Oceanic and Atmospheric Administration  Oregon State; Maureen Walzcak, University of Washington; Alexis Vizcaino, Springer Nature Group in Germany; Jason Patton, California Department of Conservation; and C. Hans Nelson and Julia Gutiérrez-Pastor, Instituto Andaluz de Ciencias de la Tierra in Spain.

on and the world.

Chris Goldfinger, a marine geologist at Oregon State University, with sediment cores.

Credit

Sean Nealon, Oregon State University.

 

CT scan images of turbidites in deep sea sediment cores. On the left, a thin bed of turbidites from a 1906 earthquake. On the right, from an earthquake about 1,500 years ago, the typical "inverted doublet beds" - a doubling or tripling of turbidite thickness. The thick sand up at the top is the San Andreas bed, with the Cascadia bed down below.

Credit

Chris Goldfinger, Oregon State University.

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Journal

Geosphere

 

Researchers discover enlarged areas of the spinal cord in fish, previously found only in four-limbed vertebrates

Nagoya University

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Researchers discovered that zebrafish have enlarged areas of the spinal cord, previously believed to exist only in four-limbed vertebrates.

 

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Credit: Naoyuki Yamamoto

Four-limbed vertebrates, known as tetrapods, have two enlarged areas in their spinal cords. The two enlargements have a correlation with the forelimbs and hind limbs, respectively. These enlargements are thought to be caused by the complex muscular system and the rich sensory networks supplying nerves to the limbs.

Meanwhile, it was long thought that fish had no enlarged areas in their spinal cords due to the absence of limbs. However, a recent study by scientists from Nagoya University in Japan has revealed that zebrafish, in fact, have enlarged areas in their spinal cords, although these areas are not visible to the naked eye.

"We thought that fish also have spinal enlargements because they have paired pectoral and pelvic fins, which correspond to forelimbs and hind limbs in tetrapods, respectively," said  Naoyuki Yamamoto, a professor at Nagoya University's Graduate School of Bioagricultural Sciences and the lead author of the study.

In a paper published in the journal Brain, Behavior and Evolution, Professor Yamamoto, along with his colleagues Ryo Takaoka and Assistant Professor Hanako Hagio, investigated whether their hypothesis was valid.

To determine whether certain regions of the spinal cord are enlarged at spinal levels innervating (supplying nerves to) the fins of zebrafish, the researchers first needed to identify which regions of the spinal cord are responsible for innervating each fin: the paired pectoral and pelvic fins, as well as the unpaired dorsal, caudal, and anal fins.

Since the innervation of pectoral, dorsal, and caudal fins had already been reported, the researchers focused on the innervation of pelvic and anal fins. They stained the entire body of the zebrafish specimen using immunohistochemistry, a technique that specifically labels the cell bodies and axons of neurons. The specimen was clarified using a modified version of the CUBIC (clear, unobstructed brain imaging cocktails) method to visualize and identify the deep spinal nerves that connect to the pelvic and anal fins.

They then created serial tissue sections along the entire length of the spinal cord. Using these sections, they examined changes in the cross-sectional areas of both the spinal cord and the gray matter, referring to the levels of the spinal cord that innervate each fin.

These analyses revealed that the spinal cord and gray matter had expanded, innervating not only paired pectoral and pelvic fins but also unpaired dorsal, anal, and caudal fins in zebrafish.

"We showed the presence of spinal enlargements in zebrafish, although they are modest and can only be detected through histological analysis," Yamamoto stated. "Furthermore, we demonstrated that these enlargements are found in all fins—that is, both paired and unpaired fins."

The findings suggest a new evolutionary theory: when tetrapods, which evolved from fish, moved onto land, only the paired fins—adapted for locomotion—transformed into limbs, while the unpaired fins disappeared.  

 

a: Whole-mount specimen of a zebrafish was immunostained for acetylated α-tubulin and cleared by the CUBIC method. The innervation of the dorsal and anal fins is visible.

b: Spinal nerve components innervating the dorsal and anal fins are traced in black for better visibility. The dorsal fin is innervated by dorsal rami of spinal nerves 9–17, while the anal fin is innervated by ventral rami of spinal nerves 13–22. (Scale bars, 1 mm)

abd cav: abdominal cavity, ana: anal fin, dor: dorsal fin

Credit

Naoyuki Yamamoto

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Journal

Brain Behavior and Evolution

DOI

10.1159/000548184 

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Identification of “spinal enlargements” correlating with paired and unpaired fins in zebrafish

 

Drinking through the generations

Flinders University

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Dr Gianluca Di Censo, Flinders University

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Credit: Flinders University

Younger generations are turning away from alcohol at unprecedented rates, with Generation Z driving a cultural shift that could reshape Australia’s drinking landscape and deliver major public health gains if the trend continues, say researchers.

A new study by Flinders University analysed over two decades of data from more than 23,000 Australians, finding that abstention from alcohol is on the rise, and weekly alcohol consumption is declining, particularly among younger cohorts.

The study used data from the Household, Income and Labour Dynamics in Australia (HILDA) survey to track drinking habits across five generational groups: the Silent Generation (1928–1945), Baby Boomers (1946–1964), Generation X (1965–1980), Millennials (1981–1996), and Generation Z (1997–2012).

It is the first study in Australia to use longitudinal data to separate the effects of age from generational change, providing robust evidence that the decline in alcohol use among young people is more than just a passing trend.

Lead author Dr Gianluca Di Censo from Flinders’ College of Medicine and Public Health and the National Centre for Education and Training on Addiction (NCETA) says the findings show a clear generational shift.

“Our research shows that over the course of their lives, Gen Z are nearly 20 times more likely to choose not to drink alcohol compared to Baby Boomers, even after adjusting for sociodemographic factors,” he says.

“This isn’t just a phase; it appears to be a sustained change in behaviour that could have long-term public health benefits.”

The study shows that, although alcohol abstinence is generally lowest in early adulthood, Generation Z shows a higher likelihood of abstaining compared to previous generations.

Not only are they more likely to abstain, but they also consume significantly less alcohol per week than older generations.

Millennials, too, are drinking less than Baby Boomers, suggesting a broader cultural shift away from alcohol.

Interestingly, while Millennials and Generation X reported drinking more per occasion than Baby Boomers, their overall weekly consumption was lower, indicating that binge drinking may still be a concern, but regular heavy drinking is declining.

Co-author Dr Kirrilly Thompson says that the findings challenge long-held assumptions about Australian drinking culture.

“For decades, alcohol has been deeply embedded in social life, but that’s changing,” she says.

“Younger Australians are growing up in a different world—one where abstaining from alcohol is increasingly normal, and where digital socialising, rising living costs, and health awareness are reshaping how people spend their time and money.”

The study also found that the Silent Generation—those born before 1946—had the highest levels of weekly alcohol consumption, even more than Baby Boomers, suggesting that while younger generations are drinking less, older Australians may still be at risk of alcohol-related harm.

The researchers say these generational trends could help inform future public health strategies.

“If we can understand what’s driving this decline in alcohol use among younger people, whether it’s economic pressures, social norms, or policy changes, we can use that knowledge to support healthier behaviours across all age groups,” says Dr Di Censo.

The study’s authors suggest that policies such as minimum alcohol pricing, restrictions on advertising, and targeted health campaigns could help reinforce these positive trends. They also emphasise the importance of continuing to focus on high-risk groups, such as adolescents who engage in binge drinking and middle-aged adults who consume large quantities weekly.

Dr Thompson adds that the findings offer a hopeful outlook.

“This research shows that change is possible. Generation Z are redefining what it means to socialise and celebrate, and they’re doing it with less alcohol. That’s something we should be paying attention to, not just as researchers, but as a society,” she says.

The paper, ‘OK Boomer: A longitudinal analysis unravelling generational cohort differences in alcohol consumption among Australians’, by Gianluca Di Censo, Kirrilly Thompson, Murthy N. Mittinty and Jacqueline Bowden was published in Addiction DOI: https://doi.org/10.1111/ADD.70201

Acknowledgements: Gianluca Di Censo, Kirrilly Thompson, and Jacqueline Bowden receive funding from the Australian Government Department of Health, Disability and Ageing to support research regarding alcohol and other drugs.

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Journal

Addiction

DOI

10.1111/ADD.70201 

Method of Research

Meta-analysis

Subject of Research

People

Article Title

OK Boomer: A longitudinal analysis unravelling generational cohort differences in alcohol consumption among Australians

Article Publication Date

2-Oct-2025